Problem: How many significant figures does $0.0661000$ have?
Solution: Identify the non-zero digits and any zeros between them. These are all significant. $0.0{661}000$ Leading zeros are not significant. $\color{orange}{0.0}{661}000$ Since there is a decimal, trailing zeros are significant. $\color{orange}{0.0}{661000}$ Counting all the significant digits gives us 6.